Occasionally a woman might notice blood stains on her undergarments or bedsheets, when she is not expecting her period. These stains can, in many instances, render the woman niddah. However, there is a tendency for the rabbi to make a lenient ruling, as there is a doubt as to whether the stain came from her at all. Therefore, one should not hesitate to ask the rabbi in cases concerning stains.*
1. Our Rabbis of Blessed Memory ruled that if a woman finds a blood stain on her clothing or on her body that she is considered niddah. Even if she felt nothing come out of her uterus and even if she immediately checked herself and found no blood she is still considered niddah.
2. She must make a Hefsek Betahara and count seven clean days and immerse in a mikveh, like any other woman who is niddah.
3. This rule applies to every adult woman even pregnant, nursing or elderly women, even if they do not regularly have periods.
4. The blood stains which the rabbis determined to give the woman niddah status must be at least the size of a bean, this is more than 20 mm in diameter which is approximately 25/32 of an inch, or a little bigger than a penny. Whether it is round or long she is impure if the stain has this area.
6. If several smaller stains were found on the woman's skin it is proper to take a stringent approach and consider her niddah if, when combined, they equal the above-mentioned size.
7. The area of separate stains found on garments is not combined to consider her niddah, rather the size of each stain is judged separately.
8. However, If the stains were found on her skin between her thighs totaling the "size of a bean" she is impure even if these stains are in strange shapes, like circles or horizontal lines.
9. Blood stains found on colored garments do not render the woman niddah. Therefore if a woman found a blood stain on her colored underwear or the like she does not become niddah, unless she did an internal examination and found herself to be niddah. This leniency applies even if she knows that the blood came from her. This leniency applies because she did not have the physical sensations normally associated with menstruation.
10. This leniency applies to any color garment whether it be light or dark and applies equally to yellow and red garments: only stains found on white garments are impure and only if they are larger than "the size of a bean".
11. A stain found on a striped garment is pure unless a stain "the size of a bean" (20 mm) is found on the white area. If a stain were found extending from one white stripe over a colored area to the next white stripe it renders the woman niddah if what is found in the white areas combine to exceed "the size of a bean," the colored area does not combine but it does not divide.
12. A woman who is constantly staining should always wear colored underwear and ignore the stains which are found on them. This equally applies to a woman who is constantly stains during her seven clean days.
13. Additionally, our Rabbis of Blessed Memory ruled that stains found on something that does not receive ritual impurity do not render the woman niddah. This applies if she sat on the ground and found blood directly underneath her and did not feel the blood coming out, even if it is clear that the blood came from her. This also applies to stone floors, stone utensils, garments smaller than six by six millimeters and to paper and nylon unless the nylon is sewn with another material.
Therefore if blood was seen on the toilet seat, on the feces or on paper or cotton "panty shields" even if it was larger than "the size of a bean" the woman is not considered niddah, especially if there is a wound which could be the source of the blood.
14. None of these leniencies apply to blood which was found on an internal examination with a checking cloth that was known to be clean. If upon such an examination the woman found the tiniest trace of blood she is impure.
15. Even though blood stains found on the skin normally render the woman niddah, she is not considered niddah if the stain was found in a location where blood from the uterus would not likely reach.
If she found blood on the bottom of her foot she or on the inside of her legs and thighs she is considered niddah.
If a stain is found on the outside of her thighs or her legs the woman is not rendered niddah.
If she found blood on her hands, whether the front or back she is niddah, since her hands are might have touched her private parts. However, if she is absolutely sure that she did not, she is not niddah.
If she found blood on her skin above the waist she is not considered niddah even if it is bigger than the size of a bean. If, however, she knows that she lifted her legs above the rest of her body she is niddah if the stain is "larger than a bean".
16. If a blood stain even larger than "the size of a bean" is found on her clothing above the belt she is pure even if she raised her legs high, since blood from her uterus would have also been found on her skin.
17. Stains found on clothing, even if found only on the external garment below the area of the belt are always render the woman niddah if they are larger than the "size of a bean" since her clothing always folds in and out.
18. If she was busy with red colored substances like ketchup or anything of the like she is not considered niddah from stains even if they are larger than "the size of a bean".
19. Since the rules regarding stains are rabbinical and the Rabbis did not want to be too strict, a lenient decision is called for even if there is a slight uncertainty concerning the stain's nature.
20. As mentioned above, a woman is not considered niddah if she was busy with substances which stain red (Ketchup, dye etc.), even if she is wearing three layers of clothing and found a stain on her bottom layer of clothing, and even if it is larger than "the size of a bean". However, if she found the stain on her skin she should be strict unless she has a wound from which she may have bled. Even if the wound has a scab on it presently, she can still assume the blood came from it if it could open. If the wound is on her shoulder and the stain is on her legs she is niddah.
21. Just as a woman can assume a blood stain came from her wound, if she found a stain she may assume that the blood is from her husband's or child's wound, even if their wounds have scabs but might open.
22. If her husband regularly bleeds from his penis she may assume that a stain is from him, even if the blood was found after having relations. Even if he bled from his penis only once she may rely that stains found on sheets are from him.
23. If the woman's husband or child finds a blood stain it is not assumed to be from the woman. Instead it is assumed to come from some other source, and the woman is not niddah.
24. A woman is considered niddah if she found an impure stain and is not sure whether she dealt with any other possible sources of stains.
25. If she was working with something red but found a black stain, she is considered niddah if the stain is " larger than a bean ". Similarly, if she dealt with black substance but found a red stain she is considered niddah. ( See the chapter which discusses which colors are pure and which are impure ). However, if she dealt with something reddish but found a stain of a different shade of red she is not niddah, (she need not compare the stain with the substance with which she was working to see if they are exactly the same color.)
27. If she dealt with a reddish substance exactly "the size of a bean" but found a stain twice the size of a bean she remains pure since the extra substance is assumed to be from another source. If the stain is larger than double "the size of a bean" she is considered niddah.
28. A woman is not considered niddah if she found a stain and if she was busy with a substance that can stain but does not remember how much she dealt with.
29. Likewise, a woman is not niddah when she found a stain larger than "the size of a bean" if she dealt with something that could stain her even if it could only make a stain less than "the size of a bean".
30. It is better to be strict and pronounce a woman niddah if she was busy with a substance less than the size of a bean and found the size of two beans.
31. A woman is only considered niddah because of a stain if the garment she was wearing is checked for stains and was found to be clean. If the garment was not checked from before she is not considered niddah if a stain is found.
32. If the woman wore a garment while she was niddah or even during the seven clean days and did not check it for stains, and when she wore it again a stain is found on it, she is not considered niddah since it can be assumed that the blood was there from before. Similarly, a woman is not considered niddah if she wore a garment before she became pregnant and found a stain on it while she is pregnant, since we assume that the blood was there from before she was pregnant.
33. Today all laundered garments are considered clean and free from stains which might have been on them. This is because modern washing machines clean off all stains and would not leave a stain so large that it would be considered impure.
34. If a woman checked herself with a clean white cloth and found even the tiniest amount of blood she is niddah whether the blood stain is round or long. This also applies even if she checked with the cloth but did not look at it right away, putting it away, instead, in a safe storage place.
35. A white cloth which was checked for stains and found clean is considered checked regardless of who did the checking. It remains in that "checked" status until it is known to have become dirty.
36. If a woman examined herself with a cloth that has not been checked and found blood on it, she is not considered niddah unless the stain is larger than the "size of a bean". Since the cloth was not checked it can be assumed that the small stain was there from before.
37. If she examined herself with a unchecked cloth and then placed the cloth near her body, but in a place where menstrual blood would not normally be found. If she subsequently found a stain on the cloth even if the stain is larger than "the size of a bean," she is not considered niddah. If, however, the cloth was placed where menstrual blood could reach then she is considered niddah.
38. If she examined herself with a checked cloth and before looking at it she put it under her thigh, if a long stain is found she is niddah, as it is assumed to have come from the examination. If a round stain is found she is not niddah, (it is assumed that the stain came from her thigh) unless it is larger than "the size of a bean." This is because a long stain definitely came from her but a round stain might have come from another source.
39. Even if a woman has become niddah from stains at regular intervals her fixed period is not uprooted and no new period has been fixed. She need not worry and separate from her husband at any interval on which stains may have occurred.
40. A woman who has examined herself internally with a checked cloth and found herself to be niddah on three separate occasions of equal intervals is considered to have a fixed interval. (see the chapter on how periods are fixed ).
* The laws of this chapter are adapted from Taharat Habayit Vol. 1 Chapter 8.